Heat-processed dehydrated bacteriologically-stable pork rind product and process for preparing same

ABSTRACT

A pork rind product capable of storage at ambient temperature and which may be used in the meat industry as a source of protein has a water content of less than 15% by weight, a fat content of less than 20% by weight and a particle size of less than 5 mm. The product is capable of rapid rehydration.

.Iadd.This application is a continuation of application Ser. No.929,425, filed Nov. 12, 1986, now abandoned; which is a continuation ofU.S. Ser. No. 824,371, filed Jan. 23, 1986, now abandoned; which is acontinuation of U.S. Ser. No. 719,969, filed Apr. 4, 1985, nowabandoned; which was a continuation of U.S. Ser. No. 604,004 filed Apr.26, 1984, now abandoned; which was a continuation of U.S. Ser. No.421,785, filed Sept. 23, 1982, now abandoned, which is a reissue of U.S.Ser. No. 383,288, filed July 27, 1973, now U.S. Pat. No. 3,922,377..Iaddend.

This invention concerns improvements in additives for food products.More particularly, it concerns such additives which are manufacturedfrom pork rind, hereinafter referred to as "rind".

Rind is employed by the meat industry in comminuted meat products andmay also be used in products in which a proportion of meat or meat-likesubstance is used. It provides an economical source of protein, and maybe employed in varying proportions depending on the legally permittedamount for that product. However, the processing of rind is usually atime-consuming and labour-intensive operation for the manufacturer. Thefresh rinds have to be stored under refrigeration, and may subsequently,if frozen, have to be thawed when required for further processing. Rawrinds may then be used but because of their high bacteriological countare normally substantially heat processed in order to arrive at a countsuitable for inclusion into comminuted products. Raw rinds, againbecause of their physiological structure, are often heat processed inorder to arrive at a softened structure suitable for inclusion intoproducts or emulsification. The rind having been reduced to anacceptable particle size may be used in this form or, alternatively, maybe combined with other proteinaceous materials, fats and additives tocreate mixed emulsions.

The processing of rind is a time-consuming and labour-intensiveoperation. Therefore, the manufacture must accurately predict hisrequirements for rind and rind emulsions in order to avoid the loss ofinexpensive protein and fats derived from rind which would have to bereplaced by other sources of protein and fats, normally more expensive.

Furthermore, rind, being a natural product, varies considerably in theproportions of such components as fat, protein and water content.

It has now been found that it is possible to process rind into adehydrated granular form in which it is microbiologically stable forextended periods and can readily and rapidly be rehydrated into aprepared ground rind, for subsequent inclusion into, for example, acomminuted meat product or, otherwise quickly and conveniently beconverted into an emulsion-type rind product with the addition ofproteinaceous materials, fats and additives.

According to one aspect of the present invention there is provided adehydrated, bacteriologically-stable, rind product having a watercontent of less than 15% by weight, a fat content of less than 20% byweight, and a particle size of less than 5 mm, the dehydrated rind beingcapable of rehydration into a rind product.

Water content may be assayed by placing a weighed sample of the materialin a constant temperature oven at 105° C. for 4 hours, allowing thesample to cool in a desiccator, reweighing and then calculating thepercentage loss of moisture.

Fat content may be assayed by solvent extraction, e.g. with petroleumspirit.

The water content is preferably in the range 4 to 9% by weight,typically from 4 to 6% by weight. The fat content is generally in therange 4 to 16% depending on the part of the pig from which the rind isobtained. It is preferred that the water and fat contents be as low aspossible, consistent with the production of a substantially stableproduct.

The dehydrated rind is mainly protein, this typically constitutingbetween 70 and 96% by weight as calculated from the nitrogen content(protein content=nitrogen content×6.25). The nitrogen content may beassayed in conventional manner e.g. after digesting a sample withsulphuric acid using a catalytic mixture of copper sulphate and sodiumsulphate.

The particle size is of great importance to the properties of theproduct. Rehydration speed decreases as particle size increases. Formost purposes, in order to combine rapid rehydration with ease ofhandling, a particle size in the range from 0.5 to 3 mm is preferable.Smaller particle sizes may be advantageous when the dehydrated rind isto be included into dried meat products, soups, and prepared foods.

The dehydrated rind has an appearance like that of demarara sugar, beingpale brown and relatively free flowing.

The dehydrated rind of the present invention has many advantages for themanufacturer of meat products and products containing meat. Iteliminates the necessity to store fresh rinds under either refrigerationor freezer conditions; the utilization of labour is substantiallydecreased with the reduction in handling and the elimination ofprolonged heat processing followed with the subsequent cooling of saidproduct.

The necessity to reduce the rind to a desired particle size iseliminated, unless the product of the present invention is manufacturedinto a mixed emulsion of such consistency that requires again areduction in particle size before the inclusion into meat products andproducts containing meat.

The time saving in providing the product of the present invention isconsiderable. The prolonged cooking and cooling cycles may beeliminated, as well as the grinding processes, in order to arrive at thedesired particle size. The product of the present invention may be readyfor use in a very short space of time as opposed to an hour or more fornormal fresh rinds. It can be made into a rind combination emulsion ofconsistent quality as opposed to the variation which may occur inquality when using a fresh rind, heat-processed or not.

The dehydrated rind can be stored for several months withoutrefrigeration in ambient temperatures of 13°-19° C., and can berehydrated in less than ten minutes; the time cycle varying dependent onthe temperature of the water used for rehydration and the degree ofagitation used during the rehydration period, but can be as short as 60seconds.

Because of the consistent and known quality of the dehydrated rind, themanufacturer of meat products and products containing meat is able toensure much more easily that his products meet the required legalstandards.

The dehydrated rind may be manufactured, according to another aspect ofthe invention, by drying fresh rind to a water content of less than 15%,at between 100°-344° C. with simultaneous removal of fat to a fatcontent of less than 15%, rapidly cooling the product and comminutingthe product to a particle size of less than 5 mm, if necessary.

The product may be dehydrated in air or in oil, or a combination of bothair and oil methods may be used, prior to cooling.

The dehydration may be effected at reduced pressure. If desired part ofthe dehydration may be effected at reduced pressure and part atatmospheric pressure.

The temperature must be carefully controlled at all stages of productionto present degradation and gelatinisation. In order to ensure reasonablyrapid dehydration, an air temperature in the upper limits of the rangepreviously indicated is preferred for the initial stage of thedehydration. The high temperature "case hardens" the rind product. Thishas been found to be advantageous in preventing gelatinisation. At thesame time, a proportion of the fat originally present in the rind isrendered off, and removed.

As the water content of the product falls, the temperature ofdehydration may be reduced and should be carefully controlled in orderto prevent degradation of the product.

It is possible to reduce the moisture content down to the final value(typically 4-6%) by careful air drying. It is, however, easier tocontrol the final drying stage, if this is carried out in heated oil,for example in a steam-heated rendering vessel. When the requiredmoisture content has been reached, the excess oil is drained away.

The product may, if so desired, be centrifuged or treated with a foodgrade oil solvent in order to reduce further the fat and oil content.

After dehydration, the product should be cooled as rapidly as possiblein minimum contact with the atmosphere. In batch processes it may beconvenient to cool first to ambient temperature before effecting furtherprocessing.

The adjustment of particle size may take place before heat processing orafter dehydration has been completed. Alternatively, a combination ofboth methods may be used.

It will generally be convenient to effect at least some adjustment inparticle size before dehydration in order to facilitate the carrying outof the dehydration process. Where the final adjustment in particle sizeis effected after completion of the dehydration the dehydrated rind maybe comminuted at ambient temperature (13°-19° C.) or, alternatively, itmay be frozen prior to comminution. Although freezing may be effected ina refrigerator or freezer, it has been found to be preferable to effectthis by treatment with a liquid gas, particularly liquid nitrogen.

Freezing with liquid nitrogen appears to result a microcrystalline-likestructure of the fat in the dehydrated rind as a result of the rapidfall in temperature. Such a structure is readily broken down oncomminution and lubrication effects, due to the fat, do not occur in thecomminutor while the product is in a frozen state. The resultingcomminuted product may them be stored at ambient temperature.

The product is rehydrated in water, preferably hot water, andrehydration rates may be increased by the inclusion into the water ofedible metallic salts for example.

At a temperature of 66°-77° C., a substantial amount of rehydrationtakes place in about 1.5 minutes with continuous agitation. The productalthough like, is not entirely identical to a fresh ground rind or aheat processed ground rind, but can replace these for most purposes. Therehydrated rind may be added to fresh meat products, for examplehamburgers and sausages. It may be added to baked meat products such aspies, cooked meats, canned meat products (e.g. canned hamburgers) pastesand soups.

It may also be incorporated into products containing meat but which arenot in themselves meat products, e.g. dried products such as driedsoups. The dehydrated rind may be added, without previous rehydration,to such products providing that during a processing cycle rehydrationoccurs before consumption.

The quantity of the product which is added to food stuffs containingmeat will depend on the requirements being met. Generally speaking atleast 5% and not more than 15% by weight, calculated on the meat, willsuffice.

It will be understood that the dehydrated product may be blended, ifdesired, with other materials, additives, stabilisers and emulsifiersemployed in the food processing art, e.g. vegetable proteins, animalproteins, or products normally associated with or added to meat productsand products containing meat.

It is a particular advantage of the dehydrated product according to theinvention that it has a long storage life at ambient temperatures. Thepresence of antioxidants and preservatives is not generally necessary,although these may be added in the concentrations customarily employedif the storage conditions are particularly severe.

In order that the invention may be better understood, the followingexample is given by way of illustration.

EXAMPLE A. Manufacture of dehydrated rind

Defatted pig rind is cut into pieces approximately 12 mm. Thismeasurement is not critical.

The rind is then loaded into a perforated drum which is enclosed in avented, insulated casing. The perforated drum rotates in the horizontalplane. Hot air is forced from both ends into the rotating drum, which isfitted with lifting baffles so that the rind is being both agitated andfalling through the hot air stream at the same time, until the productis case hardened, which at an inlet air temperature of 250° C. takesapproximately ninety minutes.

In order to advance the dehydration and sterilization with a high degreeof control, the rind is transferred to oil (or fat) contained in aheated vessel. The rind and oil (or fat) are constantly stirred at atemperature of 125° C. until the moisture content is reduced to thefinal value of 4-6%.

The now dehydrated rind is removed from the oil (or fat) and transferredto a closed vessel cooled externally by cold water. The product isstirred until its temperature is reduced to ambient temperature (13°-19°C.).

The resulting product is immersed in liquid nitrogen at about -75° C.for 3-6 minutes and is then ground to produce a final product having aparticle size of about 2 mm.

B. Rehydration of rind

Dehydrated rind manufactured according to A is rehydrated with agitationin approximately 400% of its own weight of water at 70°-77° C.containing 2% of sodium chloride and 1% of sodium polyphosphate (pH 9 in1% solution) calculated on the combined weight of water and rind.Absorption of water is approximately 400% by weight. The rehydrated rindis then cooled to at least 9° C. before utilisation.

C. Utilisation of rehydrated rind

The rehydrated rind produced according to A may then be used in themanufacture of meat products and other meat-containing foodstuffs. Thefollowing is a typical formulation for the manufacture of pork sausages,the manufacture otherwise being conventional; percentages are by weight:

    ______________________________________                                        Lean pork meat           9.5%                                                 Rehydrated rind according to B                                                                         6.5%                                                 Pork belly               25%                                                  Pork fat                 11%                                                  Beef flank               13%                                                  Seasoning                2.675%                                               Sodium polyphosphate*    0.325%                                               Rusk                     9%                                                   Farina                   2%                                                   Sodium caseinate         2%                                                   Milk powder              1%                                                   Water                    18%                                                  ______________________________________                                         *Having a pH of 7 in 1% solution.                                        

I claim:
 1. A heat-processed, .Iadd.case-hardened, .Iaddend.dehydrated,bacteriologically-stable, pork rind product capable of rapid rehydration.Iadd.without gelatinization to a rind-like product suitable for humanconsumption, said dehydrated pork rind product .Iaddend.having a watercontent from about 4% to about 15% by weight, a fat content from about4% to about 20% by weight, a protein content between 70% and 96% byweight, and a particle size from about 0.5mm to about 5mm, saidpercentages being based on the total weight of the product.
 2. Aheat-processed, .Iadd.case-hardened, .Iaddend.dehydrated,bacteriologically-stable, pork rind product capable of rapid rehydration.Iadd.without gelatinization to a rind-like product suitable for humanconsumption, said rehydrated pork rind product .Iaddend.having a watercontent from about 4% to about 9% by weight, a fat content from about 4%to about 16% by weight, a protein content from about 70% to about 96% byweight, and having a particle size from about 0.5mm to about 3mm, saidpercentages being based on the total weight of the product.
 3. A processfor the manufacture of a bacteriologically-stable pork rind productcapable of rapid rehydration which comprises the steps of drying freshpork rind to a water content from about 4% to about 15% by weight at atemperature between 125° and 344° C. with simultaneous removal of fat toa fat content from about 4% to about 20% by weight .Iadd.to form acase-hardened non-gelatinizing pork rind product, .Iaddend.cooling andcomminuting the dried product to a particle size from about 0.5mm toabout 5mm.
 4. A process as defined in claim 3 wherein the cooleddehydrated rind product is frozen with liquid nitrogen prior tocomminuting.
 5. The process of claim 3 wherein said drying is effectedby air drying the pork rind product for a time sufficient to effect casehardening of said product and then oil drying the case hardened product..Iadd.
 6. The product obtained by the process of claim 3 having aprotein content between 70% and 96% by weight. .Iaddend. .Iadd.7. Theproduct obtained by the process of claim 4 having a protein contentbetween 70% and 96% by weight. .Iaddend. .Iadd.8. The product obtainedby the process of claim 5 having a protein content between 70% and 96%by weight. .Iaddend.